The question is relative and subjective. Because of the many factors involved, there are none that are "best" as all have their weaknesses from time to time. In my area, T-Mobile appears to have better coverage but just a tad south Verizon works better. As far as customer service reps, they too have bad days and they too suffer from lack of training. Those places with higher turnover are even more so. I'm not negating the possibility that the service rep might be a complete and total failure at this particular job, just that there are other explanations. Also working in a potentially high stress job day in and day out with users who on occasion can't distinguish between their left and right sides then blame you doesn't help matters any.